IBM had very little patentable subject matter in the original 5150 design, and anything they could patent would have been subject to an antitrust decree that legally required them to, in Tim Kulak[0]'s words, "work for free". That's why they focused on copyright in the BIOS so heavily.

Also, none of this impacts Linux, beyond the fact that IBM clones were ubiquitous by the time Linus started writing the kernel. If IBM clones weren't around, Linux probably would have originally ran on an Amiga. It was very much expected that personal computers would run anything compiled for the CPU, mainly because the companies making them shipped very little software. I guess you could say that Linux was possible because there were PCs to buy - otherwise we'd be stuck with BSD or GNU running on computers we had to rent. But even then, what IBM did here was not directly open the floodgates to a Free OS, they just accidentally opened the floodgates to a bunch of companies entering the PC market by blatantly and legally ripping them off.

[0] Kulak is a Russian word for owners of rural land that refused to join the Soviet collectivization regime, which was then later applied to basically anyone accused of not meeting the hilariously awful production quotas Stalin put on shit. Despite this awful history, I'm appropriating the term because A) it's a good pejorative for land-owning nobility and B) it almost rhymes with Cook.